Major problem with Macros -Powerpoint update?

[Cosmo]

I am having a huge problem right now, all of the PPT programs I have written are no longer running on my or my client's machines, I am guessing due to a recent PowerPoint 2007 update. I get the message "Object Library invalid or contains references to object definitions that could not be found" when I try to run them, and it highlights a function definition (it is highlighting the entire parameter list:
[vba]
Private Function GetSettingsDialog(ByRef useTemplate As Boolean, _
ByRef pullDataIntoMaster As Boolean, _
Optional ByVal yearQuarterKey As Integer = 0, _
Optional ByVal offsetValue As Integer = 0, _
Optional ByRef fileToClose As PowerPoint.Presentation = Nothing, _
Optional ByVal INONumber As String = "", _
Optional ByVal Version As Integer = 0, _
Optional ByVal Revision As Integer = 0)
[/vba]
The only parameter that is not a simple datatype is PowerPoint.Presentation. If I take that line out, it highlights a different function call and highlights a boolean constant used as a default for that parameter.

Does anyone know if there was a recent update to Office/Powerpoint which is causing problems?

I'll post more if I make any progress in detailing where the issue is, but I'm at the 'tearing my hair out' stage right now.

EDIT - IT doesn't seem to be that function call specifically - if I copy that function call into a blank document, it causes no errors.

Is there any way to determine which library might be the cause of the issue?